(a) Field of the Invention
The present invention relates to a roll forming method and a shaped beam produced by using the same. More particularly, the present invention relates to a roll forming method and a shaped beam produced by using the same that prevents generation of non-uniform dents due to heel tap at an inward surface of a curvature when a shaped beam of a closed section produced through a roll forming process is formed to have the curvature.
(b) Description of the Related Art
Generally, a roll forming method is a method in which a coil is uncoiled and the uncoiled coil is bent to various shapes by passing through a roll forming unit. The roll former unit includes a plurality of roll formers that are sequentially disposed, and each roll former is provided with an upper forming roll and a lower forming roll. The roll forming method is used for manufacturing beams of linear type (particularly, a bumper beam for a vehicle) which is bent to the various shapes.
FIG. 1 is a schematic diagram of a typical roll forming system and steps of a roll forming method.
Referring to FIG. 1, the typical roll forming system and method thereof includes an uncoiler 1 at a front portion of a process line, and the uncoiler 1 performs an uncoil step S1 at which a coil 10 is uncoiled.
A straightener 2 is provided at the rear of the uncoiler 1 in the process line and performs a straightening step S2 at which the coil uncoiled from the uncoiler 1 is straightened to a panel 20 of plate shape.
A brake press 3 is disposed at the rear of the straightener 2 in the process line and performs a piercing step S3 at which a plurality of holes for assembling is formed at the panel 20 supplied from the straightener 2.
A roll forming unit 4 including at least seven roll formers R1-R7 is disposed at the rear of the brake press 3 in the process line. The roll forming unit 4 performs a roll forming step S4 at which the panel 20 passing through the uncoiler 1, the straightener 2, and the brake press 3 is sequentially bent such that a shaped beam 30 having a desired closed section is formed.
A laser welding device 5 is disposed at the rear of the roll forming unit 4 in the process line and performs a welding step S5 at which a laser beam outputting from a laser oscillator 5a is irradiated to a welding portion of the shaped beam 30.
In addition, a round bender 6 is provided at the rear of the laser welding device 5 in the process line and performs a bending step S6. At the bending step S6, the shaped beam 30 passes through a plurality of bending roll units disposed along a desired curvature such that the shaped beam 40 having the curvature is formed.
FIG. 2 is a side view of a typical round bender.
Referring to FIG. 2, the round bender 6 includes five bending roll units.
A first bending roll unit BR1 includes a pair of bending rolls and is disposed at a front portion of a roll frame 6a in the process line. The first bending roll unit BR1 guides the shaped beam 30 passing through the welding step S5.
A second bending roll unit BR2 includes a pair of bending rolls and is disposed at the rear of the first bending roll unit BR1 on the roll frame 6a. The second bending roll unit BR2 rolling-supports the shaped beam 30 along the curvature direction.
In addition, third, fourth, and fifth bending roll units BR3, BR4, and BR5 respectively include a pair of bending rolls, and are sequentially disposed at the rear of the second bending roll unit BR2 on the roll frame 6a along the curvature. The shaped beam 30 passes through the third, fourth, and fifth bending roll units BR3, BR4, and BR5 sequentially such that the shaped beam 40 having the curvature is formed.
A cutting press 7 is disposed at the rear of the round bender 6 in the process line and performs a cutting step S7 at which the shaped beam 40 is cut in a size of the finished product.
FIG. 3 is a perspective view of a shaped beam produced by a typical roll forming system and a method thereof.
Referring to FIG. 3, the shaped beam 50 produced by the typical roll forming system and the method thereof includes the closed sections at an upper portion and lower portion thereof, and is formed to have the curvature along a length direction thereof. In addition, widths of the upper closed section and the lower closed section are different.
The shaped beam 50 can be applied to components of a vehicle body or various industrial beam members, and particularly, to a bumper beam of a vehicle.
A plurality of non-uniform dents D due to heel tap can be generated at a surface of the lower closed section facing toward an inward of the curvature in the shaped beam 50 as shown in FIG. 3, when the shaped beam 50 is formed to have the curvature through the round bender 6. The dent may deteriorate impact strength of the shaped beam 50.
In a case that such a shaped beam 50 is applied to the bumper beam of the vehicle, a hole H is bored at one side of the shaped beam 50 and a towing hook pipe (not shown) is inserted in the hole H. At this state, the shaped beam 50 and the towing hook pipe are welded by using CO2. At this time, the non-uniform dent D on the shaped beam 50 causes non-uniform surfaces between the towing hook pipe and a welding portion of the shaped beam 50, and bad welding may occur.
In order to secure welding quality of the shaped beam 50 and the towing hook pipe (not shown), all the welding portions should be inspected and additional welding should be performed at bad welding portions. However, theses may deteriorate productivity in automated processes.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.